A conventional incubator is described in Japanese Patent Laid-Open No. 2012-223320. In the conventional incubator described in Japanese Patent Laid-Open No. 2012-223320, a flat container-shaped bed base is provided on an incubator base. The incubator base is provided with a fixed wall member (or fixed baby guard) which generally forms a wall member on the head side of an infant, a leg-side movable wall member (or movable baby guard) which generally forms a wall member on the leg side of the infant, a left movable wall member (or movable baby guard) which generally forms a wall member on the left side of the infant, and a right movable wall member (or movable baby guard) which generally forms a wall member on the right side of the infant. These wall members are provided in a substantially rectangular shape as a whole when viewed from above. An infant accommodation space having a substantially rectangular parallelepiped shape with an open upper surface is constituted by the bed base (in other words, a mattress on the bed base), the one fixed wall member, and the three movable wall members. Note that each of the one fixed wall member and three movable wall members can take a substantially rectangular shape and can be substantially transparent. In addition, each of the three movable wall members and one fixed wall member can be formed, substantially as a whole, from a substantially transparent plastic plate. Each of the three movable wall members can pivot forward and backward, about pivot support shafts on the left and right sides or the front and rear sides provided in a region including a lower side and its vicinity in the substantially upward position (to be referred to as “the above-described upward position” hereinafter), between the above-described upward position and the substantially downward hanging position (to be referred to as “the above-described hanging position” hereinafter).
In a conventional incubator, the plate thickness of each of the three movable wall members and one fixed wall member for forming an open type incubator is approximately 5 mm. On the other hand, when an operator lays an infant, for example, a newborn infant down on the mattress of the open type incubator or holds up the infant from the mattress, he/she inserts his/her arm to the infant accommodation space. In this case, the arm of the operator can abut against the upper end portion of at least one of the three movable wall members and one fixed wall member. There is the risk that if the arm of the operator abuts against the upper end portion of the wall member relatively hard, the operator feels a pain or the arm gets hurt.